Fiber reinforced plastic members

ABSTRACT

The present invention relates to FRP members, the apparatus and process for making same. The FRP members are reinforced with helical strands of reinforcing material disposed in expanded helices of opposite hand, the helices of each hand being contained in discrete layers. The lead angle of each helix may be constant or varied along the length of the member independently of whether the member is cylindrical or tapered in order to provide the desired structural characteristics. The process comprises impregnating the reinforcing strands with resin and wrapping those strands onto a mandrel by apparatus in which relative rotational as well as relative translatory movement between the mandrel and a winding head may be effected to wrap the strands onto the mandrel. At least one relative movement may be selectively varied to effect the desired lead angle to the helically disposed reinforcing strands along the length of the mandrel.

This is a division of application Ser. No. 720,907, filed Sept. 7, 1976,now U.S. Pat. No. 4,089,727.

BACKGROUND OF THE INVENTION

Golf clubs, fishing rods and even utility poles are being made fromresinous material incorporating a fiber, or fibrous, reinforcement--morespecifically, such goods are being made from liquid, thermosettingresins incorporating roving, fabrics or matted materials and thereinforcement. Goods made from fiber reinforced resin material are,appropriately, designated as FRP members, and one of the principle waysin which FRP members are made is by helically winding a succession ofresin impregnated reinforcing strands about a mandrel.

According to prior art techniques, one or more strands, or ribbons, ofthe reinforcing material is wound onto the mandrel, beginning at a firstend thereof, in a helical configuration of one hand, and one or moresuccessive strands, or ribbons, is wound, beginning at the second endthereof, onto the mandrel in a helical configuration of opposite hand.These steps are thereafter repeated with successive strands being woundadjacent the previous winding of like hand until the mandrel iscompletely covered and the desired thickness is acquired. Thereafter themember is cured.

By employing a successive series of wraps at opposite hand eachreinforcing strand after the first lay is crimped as it accommodates toeach crossover of previously laid strands. This crimping induces astress concentration at the crossover when the finished product isstressed and also creates a small interstice where only the resinexists. Overall, this arrangement cannot, therefore, achieve thedesideratum in mechanical properties which should be available from thematerial employed.

In addition, winding of the reinforcing strands has heretofore beenaccomplished by the use of winding heads that move at a constant ratealong the mandrel as the latter rotates at a constant rate. Accordingly,if the mandrel tapers, say from the butt to the tip, the lead angle ofthe helical wrap will progressively increase from the butt to the tip.As the lead angle increases, the orientation of the reinforcing wrapchanges to increase the flexural resistance provided by the reinforcingmaterial. For many applications, such as with fishing poles, it ishighly undesirable to increase flexural resistance in the tip portion ofthe rod.

Moreover, when the lead angle increases the torsional resistancedecreases, and for many applications, notably as with golf club shafts,it is highly undesirable to decrease torsional resistance in the tipportion.

It must be appreciated that the FRP members to which the subjectinvention is directed are those which include reinforcing filamentsdisposed in an expanded helix and not those in which the filaments areall wound in a tight spiral where each wrap of a reinforcing filamentengages the previous wrap of that same filament. Nor is the subjectinvention directed to FRP members in which the reinforcing filaments areeither all longitudinally for a configuration of reinforcing filamentsthat are disposed in part longitudinally and in part in the aforesaidtight spiral.

SUMMARY OF THE INVENTION

It is, therefore, a primary object of the present invention to providean FRP member in which discrete layers are formed by reinforcingfilaments disposed in expanded helices of common hand in order toobviate crimping of the reinforcing strands at crossovers and also toeliminate the resulting interstices.

It is another object of the present invention to provide an FRP member,as above, in which the lead angle of the helically disposed reinforcingstrands can be selectively varied along the length of the member inorder to provide the desired balance of hoop strength, flexuralstiffness and torsional stiffness along the length of the member.

It is a further object of the present invention to provide a method bywhich to make FRP members, as above.

It is a still further object of the present invention to provide novelapparatus that is relatively inexpensive to build, operate and maintain,and which operates according to the method hereof, in order to produceFRP members embodying the concepts of the present invention.

These and other objects, together with the advantages thereof overexisting and prior art forms, which will become apparent from thefollowing specification, are accomplished by means hereinafter describedand claimed.

In general, the process of the present invention is directed to themanufacture of FRP members which can be formed by wrapping strands ofresin impregnated reinforcing material helically about a mandrel, curingthe resin and removing the finished member from the mandrel. Thedirection and rate of relative movement between the rotating mandrel onwhich the impregnated reinforcing strands are wrapped and the windinghead which feeds the strands onto the mandrel are coordinated to achievethe desired disposition of the helically wrapped reinforcing strands atany given section along the FRP member being made thereby.

The novel apparatus employed to practice the aforesaid method andproduce FRP members embodying the concept of the present inventioneffects relative axial as well as rotational movement between themandrel and the winding head--the rates of at least one of theserelative movements being selectively varied to provide the desiredhelical lay of the reinforcing filaments from section to sectionthroughout the FRP member.

One preferred, and two alternative, embodiments of apparatus by whicharticles embodying the concept of the present invention may be made,together with an exemplary form of such an article, are shown by way ofexample in the accompanying drawings and described in detail, along withthe method of the subject invention, without attempting to show all thevarious forms and modifications in which the invention might beembodied; the invention being measured by the appended claims and not bythe details of the specification.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a tapered mandrel which depictsthe change in the lead angle of the helically disposed reinforcingfilaments when applied according to the prior art apparatus, methods andtechniques;

FIG. 2 is an elevation of a portion of a tapered mandrel which depictsthe expanded helical lay of reinforcing filaments thereon when woundaccording to prior art methods, apparatus and techniques--for claritythe mandrel is only partially covered by said reinforcing filaments;

FIG. 3 is a partial cross section taken substantially on line 3--3 ofFIG. 2;

FIG. 4 is a view similar to FIG. 1 but depicting, as a selected lay, aconstant lead angle for the helically disposed reinforcing filamentswhen wound onto a tapered mandrel according to the concepts of thepresent invention;

FIG. 5 is a view generally similar to FIG. 3 but depicting the discretelayers of filaments achieved when wound onto a mandrel according to thepresent invention;

FIG. 6 is a schematic, frontal perspective of an apparatus embodying theconcept of the present invention, and capable of performing the methodthereof, which, for clarity, is depicted as winding a portion of thereinforcing filaments onto a tapered mandrel--it being understood thatsaid apparatus is capable of winding an entire discrete layer at onepass;

FIG. 7 is a schematic rear perspective of the apparatus depicted in FIG.5;

FIG. 8 is an end elevation of the winding head and supporting mechanismby which the reinforcing filaments are directed to the rotating mandrelby the apparatus depicted in FIGS. 4 and 5;

FIG. 9 is an enlarged perspective view of a portion of the filamentwinding mechanism depicted in FIG. 7 and partially broken away to depictthe discrete layers in which the reinforcing filaments of common handare being wound onto the mandrel and to depict the means by which toanchor the reinforcing strands between relative passes of the mandreland winding head;

FIG. 10 is a schematic perspective of an alternative embodiment ofapparatus according to the concept of the present invention, and capableof performing the method thereof; and,

FIG. 11 is a schematic perspective of another alternative embodiment ofapparatus according to the concept of the present invention, and capableof performing the method thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

By way of background, an FRP member may be made according to prior arttechniques on a mandrel, even a tapered mandrel as identified generallyby the numeral 10 in FIGS. 1 and 2 of the attached drawings. It will benoted that mandrel 10 tapers from the butt 11 to tip 12, and anexemplary reinforcing strand 13 is emphasized in FIG. 1 to depict thehelical orientation which results when the strand is wound onto amandrel that is rotated at a constant rate while the winding head movesalong the mandrel at a constant rate. As depicted, the lead angle α inproximity to the butt 11 is lesser than the lead angle β in proximity tothe tip 12. This occurs even though the distance along which the windinghead moves during one revolution of the mandrel remains constantthroughout the length of the mandrel because the diameter of the mandrelgets smaller.

To explain, the distance along which the winding head moves during onerevolution of the mandrel can be considered as the side of a righttriangle opposite the lead angle; the filament wound onto the mandrel isequivalent to the hypotenuse of that triangle; and, the averagecircumference of the mandrel along the distance traveled by the windinghead during the referenced revolution of the mandrel is equivalent tothe side adjacent the lead angle represented in the aforesaid righttriangle. Because the circumference of the mandrel is a direct functionof its diameter, and because the diameter gets progressively smaller asthe winding head moves from the butt toward the tip, the tangent of thelead angle also progressively increases, as does the angle itself.

Test results clearly demonstrate that an increase in the lead angle ofthe reinforcing filaments in a member effects a corresponding increasein the flexural stiffness of that member. As such, if an FRP member madeon a mandrel according to the prior art techniques were to be used as afishing rod, it would be found that the flexural stiffness of the rodincreases toward the tip--the exact opposite of the desired result.

Test results have also revealed that the greatest torsional stiffness isachieved when the lead angle of the reinforcing filaments isapproximately 45°. Thus, were the resulting FRP member to be used as agolf club shaft, the torsional stiffness would vary along the length ofthe shaft as the lead angle varied above or below 45°--also anundesirable result.

Two further, though related, deficiencies inherent to FRP members madeaccording to the prior art concepts of filament winding are depicted inFIGS. 2 and 3. In FIG. 2 six successive wraps, designated as W₁ throughW₆, are depicted. As can best be observed in FIG. 3, each successivewrap is crimped, as at 14, when it crosses over the edge of thepreviously deposited strand, or strands, leaving an interstice 15 inwhich only the resin will exist. Even though a plurality of strands maybe wound at one time--three are depicted in FIGS. 2 and 3--as eachsuccessive wrap is applied it will have crimped over the previouslyapplied wraps until the mandrel is covered. Should the wrapping processcontinue to apply successive layers, corresponding crimps andinterstices will also occur in the successive layers.

The foregoing problems, which are inherent to the prior art techniques,are obviated by the present invention, and as will become apparent fromthe detailed description of the apparatus hereinafter set forth, an FRPmember can be made in which the reinforcing filaments of each hand liein discrete layers without crimping and without the resultinginterstices. FIG. 5, for example, depicts four such discrete layers--L₁through L₄ --the alternate layers being of opposite hand. The presentinvention also permits the lead angle to remain constant throughout thelength of the member irrespective of whether the mandrel is cylindricalor tapered, as represented by FIG. 4, wherein the mandrel 31 of theapparatus 30 hereinafter described in conjunction with the apparatusdepicted in FIGS. 6 through 9 is schematically represented with a singlewrap of a reinforcing strand 71 to show the constant lead angle α alongthe full extent of the mandrel. Alternatively, the lead angle may bealtered according to a preselected pattern.

References to FIGS. 6-9 reveals one embodiment of an apparatus indicatedgenerally by the numeral 30 by which to fabricate an improved FRP memberaccording to the concept of the present invention.

As best seen in FIG. 6, a mandrel 31 of tapered section is rotatablymounted between the live spindle 32 and a dead spindle 33. The deadspindle 33 may be adjustably secured along a track 34 to accommodatemandrels of various lengths, and the live spindle 32 is rotated by anoperative connection with a motor 35. As shown, a drive belt 36 connectsthe motor 35 to a gear reducer 38 through variable speed pulleys 39 and40 which may be manually operated by knob 41, which changes thediameters of pulleys 39 and 40 to control the speed plateau at which themotor pulley 39 drives the input pulley 40 on gear reducer 38.Similarly, the output pulley 43 of the gear reducer 38 may be connectedto the driven pulley 44 on the shaft 45 of the live spindle 32.

Wheels 46 presented from the horizontal base plate 48 of a trolley 50are movable along tracks 51 and 52 formed by angle irons on the frame 53of apparatus 30. An arm 54 is secured to, and extends downwardly from,the base plate 48 of trolley 50. One link 55 of a chain drive 56 issecured to the trolley 50, as by pin 57, and the chain itself is reevedabout registered sprocket wheels 58 and 59. The idler sprocket 58 ismounted at one end of the frame 53 and the drive sprocket 59 is securedto a shaft 60 rotatably mounted at the opposite end of the frame 53where it is rotated by a second motor 61 connected through gear reducer62 and chain drive 63 to a second sprocket 64 on shaft 60.

To reciprocate the trolley 50 the sprocket wheels 58 and 59 may bemounted on cantilevered axles, and the pin 57 may be vertically slidablein arm 54 in order to follow the link 55 as it traverses the upper andlower runs 56A and 56B, respectively, of the chain drive 56.Alternatively, a pair of opposed micro switches 65 and 66, as depictedin FIG. 7, may be actuated by trip arms 68 and 69, respectively, carriedon the arm 54 to reverse the motor 61 and thereby reciprocate thetrolley 50.

The trolley 50 carries an immersion tank 70 within which the reinforcingstrands 71 are impregnated with the desired resin 72. The particulartype of resin selected will be chosen for its characteristics withrespect to the specific service conditions it will need to endure. Amongthose resins generally suitable for FRP members are the polyesters, thevinylesters and the epoxies. Additional factors which may be consideredin selection of the resin are viscosity, gel time, strength, moduli,shrinkage after curing and cost. Ingredients such as pigments, catalystsand fillers are common additives to a resin mixture, and the term resinas used hereinafter is intended to include any mixture of ingredientsgenerally suitable for FRP members. The foregoing resins are generallycured by heat, and the reaction is ordinarily initiated in the range of250° to 280° F. (121° to 138° C.), but because the reaction isexothermic, the temperature may rise to over 400° F. (204° C.) and it istherefore understood that the temperature ranges will vary with respectto the type of resin selected.

As can be seen by reference to FIGS. 6 and 7, a plurality of continuousstrands of fiber reinforcing such as glass, graphite or other filaments,either natural or synthetic, are singularly and/or collectivelydesignated by the numeral 71.

In order to achieve the fullest possible impregnation of the resin intothe reinforcing strands 71 the strands are fully immersed within theresin reservoir in the tank 70. The strands 71 pass over a separatingand aligning comb 73, beneath an immersion bar 74 within the reservoirof resin 72 in tank 70 and then upwardly out of the tank 70 over a firstbar 15, through orifices 76a in bar 76 which control the resin contentin the laminate, and over a guide comb 77.

The winding head 80, which directs the reinforcing strands 71 onto themandrel 31 and which is best seen in FIGS. 8 and 9, is supported on alocator plate 81 which is also carried by trolley 50 and extendsoutwardly from the tank 70. The winding head 80 fits within asemicircular recess 82A and is secured to the locator plate 81 by nutand bolt combinations 83 and 84 which are connected through arms 85 and86 extending diametrically outwardly from the mounting plate 88. Asecond recess 82B may also be provided in the locator plate 81 to permitmounting a second winding head, not shown.

The most uniform results are achieved when the various reinforcingstrands 71 are wound onto the mandrel 31 under substantially the sametension, and it has been found that sufficient uniformity results whenthe strands being fed to various sectors of the winding head 80 areselectively routed across combs which tend to equalize the frictionalresistance applied to the individual strands 71.

For example, as the strands 71 which are to feed the three to fouro'clock sector of the winding head 80 leave the guide comb 77, they passacross friction combs 90A and 90B at rather obtuse angles before beingturned sharply through an acute angle at friction comb 90C into thethree to four o'clock sector where they are directed by guide pins 91,92 and 93 onto the mandrel 31.

Those strands 71 being fed into the five to six o'clock sector of thewinding head 80 pass over friction combs 90A, 90B and 90C at obliqueangles before being turned through a less severe acute angle by comb 90Dbefore being directed by pins 94 and 95 on the winding head 80 onto themandrel 31.

Those strands 71 being fed into the eleven to two o'clock sector areturned sharply through a reverse curve by both combs 90E and 90F afterleaving the guide comb 77 in order to increase the frictional resistancethereagainst in order to compensate for their closer proximity to theimmersion tank 70 before they are directed by guide pins 96 through 100in the winding head 80 in the eleven to two o'clock sector.

The strands 71 being fed into the nine to ten o'clock sector pass at anobtuse angle across comb 90G and at an acute angle across comb 90Hbefore being directed by pins 101 and 102 in the winding head 80 ontothe mandrel 31.

Finally, those strands 71 being fed into the seven to eight o'clocksector pass across both combs 90G and 90H at an obtuse angle beforebeing turned at a moderately acute angle by comb 90J toward pins 103 and104 in the traverse head 80 onto mandrel 31.

In the embodiment depicted in FIGS. 6-9 the trolley 50 is moved at aconstant speed by a motor 61 so that the winding head 80 will move at acorrespondingly uniform rate along mandrel 31. However, depending uponthe taper, or compound tapers, of mandrel 31 it may be necessary toadjust the rotational speed of the mandrel in order to achieve thedesired lead angle for the helical wind of the reinforcing strands 71thereon. Should it be desired to maintain a constant lead angle, asdepicted in FIG. 4, the mandrel 31 will be required to rotate at anincreased rate as the diameter of the mandrel decreases.

One manner in which this result is effected is best depicted in FIG. 7.A cam plate 105 is secured to the apparatus 30, and a cam follower 106rolls along the cam surface 108. The follower 106 may be secured to arack 109 which rotates a pinion 110 on the control shaft 111 of a linearpotentiometer 112 connected in series with the DC motor 35 (FIG. 6)which rotates the mandrel 31. Thus, by coordinating the inclination ofthe cam surface 108 to the taper, or tapers, of the mandrel 31, themandrel can be rotated at varying, but controlled, rates to achieve thedesired lead angle, or angles, for the reinforcing strands helicallywrapped thereon. The base rate, or plateau, at which the mandrel rotatescan be selected by virtue of the variable speed pulleys 39 and 40, andthe configuration of the cam surface 108 will control the speed withreference to that plateau. Thus, selection of the plateau determines thebasic lead angle and the cam surface 108 determines lead anglevariations, if any, with respect to the basic lead angle. The lead anglemust be at an angle less than 90°--an angle as large as 88° has beensuccessfully applied for the subject apparatus. While most applicationwill require the lead angle of the reinforcing filaments to fall withinthe range of 88° to approximately 45°, it is expected that someapplications will require FRP members in which the lead angle ofreinforcing filaments can approach approximately 10°. It should,however, be understood that FRP members to which this invention isdirected employ an expanded helix; thus, the lead angle for reinforcingstrands in FRP members embodying the concept of the present inventionwill not approximate 90°.

Referring again to FIG. 6 it will be noted that a first collar 113 isprovided on the mandrel 31 in proximity to the butt end 114 thereof anda second collar 115 is provided in proximity to the tip 116 thereof. Thespace between the collars 113 and 115 delineates the axial extent of theFRP member being made on the mandrel 31, and the space beyond thecollars is the waste on which the strands 71 are anchored preparatory toapplying a discrete layer of opposite hand.

In order to assure a proper anchoring of the strands exteriorily of thecollars 113 and 115 rather sharp depressions 118 and 119 are provided,one at each end of the cam surface 108. The depressions 118 and 119actuate the potentiometer 112 to effect a sharp increase in therotational speed of the mandrel 31 and are located such that thisincrease occurs when the winding head 80 is applying the strands 71exteriorily of the collars 113 and 115, thus assuring sufficientoverlapping of the strands to anchor them preparatory to the applicationof the successive wrap.

It must be appreciated that a sufficient number of strands arepreferably fed into the winding head 80 so that a discrete layer ofreinforcing strands will cover the mandrel at one pass. In this way therotational direction of the mandrel need not be reversed to applysuccessive discrete layers of opposite hand with each pass of thewinding head along the mandrel. In this regard please note the detailsin the cut-away section of FIG. 9, wherein the discrete layer L₁ isbeing overlaid with a discrete layer L₂.

It is, of course, possible to apply a lesser number of strands, but inorder for discrete layers to be applied it would then be necessary toreverse the rotational direction of the mandrel with each pass until adiscrete layer was formed. This requires extremely exacting coordinationbetween rotation of the mandrel and axial movement of the winding headin order that the successive strands would juxtapose to achieve eachdiscrete layer desired. It will be appreciated that the difficulty ofachieving juxtaposition by the successive wraps is further compounded bythe necessity of introducing a dwell in the relative axial movementbetween the mandrel and the winding head as the mandrel continuesrotating to anchor the strands before initiating the successive pass.Thus, considerable complications can be avoided simply by applying adiscrete layer with each pass, as is readily accomplished with thesubject apparatus.

It should also be appreciated that the number of strands required simplyto cover the butt portion 114 between the collars 113 and 115 of themandrel 31 may bunch somewhat when being wound onto the tip 116. Thishas been found to be perfectly acceptable and in no way denigrates theadvantages achieved by the present invention over the prior art.

In the foregoing embodiment the rotational rate of the mandrel wasvaried in relation to the constant rate at which the winding headaxially traversed the mandrel in order to achieve the desired lead anglefor the helical lay of the reinforcing filaments. It is also possible tovary the rate at which the winding head traverses the mandrel whilerotating the mandrel at a constant rate. One embodiment by which thisalternative has been achieved is schematically depicted in FIG. 10.

The alternative apparatus 200 represented in FIG. 10 rotates a mandrel201 between live and dead spindles 202 and 203, respectively, and thelive spindle 202 is rotated at a constant speed by a motor means notshown.

The winding head 204 is presented from a locator plate 205 that issecured to an arm 206 which extends vertically downwardly from one endof the horizontal base plate 208 on trolley 209.

An immersion tank 210 is carried on the base plate 208 of the trolley209, and the reinforcing strands 211 fed from a creel of spools 212 passacross a separating and aligning comb 213 through the resin bath 214 andout over a bar 215, through orifices 216a in bar 216 for control of theresin content in the laminate, and finally over guide comb 217 to feedthe various sectors of the winding head 204, as hereinbefore explainedin conjunction with the description of the previously describedapparatus 30.

The trolley 209 is movable along, and stabilized by, a trackway 218comprising a portion of the frame for the apparatus 200. In theembodiment depicted, the trackway has upper and lower rails 219 and 220,respectively, interconnected by vertical tie bars 221. Downwardlydirected rollers 222 carried on the base plate 208 engage the upwardlydirected surface 223 on rail 219, and upper, lateral, stabilizingrollers 224 and 225 engage the opposite sides 226 and 228 of the upperrail 219. A pair of lower, lateral, stabilizing rollers 229 and 230,which are carried on a horizontal flange 231 extending from the arm 206beneath the lower rail 220, engage the lateral sides 232 and 233 of thelower rail 220.

That length of a chain 235 which extends between orienting pulleys 236and 238 is connected to the trolley 209, as at 237, and moves it alongthe trackway 218. That end of the chain 235 which extends beyondorienting pulley 238 is connected to a counterweight 239, and that endwhich extends beyond orienting pulley 236 is connected to a timing cam240.

The cam 240 is driven by a motor 241 connected thereto through a gearreducer 242, and the configuration of the cam 240 is determined so thatthe throw, or eccentricity, it provides to the chain 235 at everyinstant during rotation of the cam by motor 241 is coordinated with thelocation of the winding head 204 along the axial extent of the mandrel201, thereby controlling the traversing speed of the winding head as itmoves axially along the mandrel. The counterweight 239 assures that thetrolley 209 will move to the full extent permitted by the cam 240. Inthis way one can predetermine the lead angle at which the reinforcingstrands 211 are wound onto the mandrel 201.

If a discrete layer of reinforcing strands are applied to the mandrel ateach pass of the winding head, the mandrel may be rotated at a constantspeed in one direction, but the motor 241 which moves the trolley 239must be reversed at the conclusion of each pass. This can beaccomplished by means well known to the art, exemplary of which would bethe use of micro switches, not shown, engageable by the trolley as itreaches each end of its desired travel.

Variation of the rate at which the winding head moves with respect tothe mandrel, while maintaining the rotational rate of the mandrelconstant, can also be achieved by axial movement of the mandrel past afixedly located winding head. This concept finds particular suitabilitywhen the FRP member requires a relatively large number of reinforcingstrands, and a schematic representation of such an apparatus isidentified generally by the numeral 300 in FIG. 11.

A plurality of winding heads 301 are fixedly supported on a stanchion302, and each is fed with a plurality of reinforcing strands 303 frombanked creels 304, the reinforcing strands passing through bankedimmersion tanks 305. In order to supply a sufficient number ofreinforcing strands it may be necessary to bank the creels and immersiontanks on both sides of the stanchion 302 rather than just on the oneside, as depicted in FIG. 11.

A mandrel 306 is rotatably mounted between a live and a dead spindle 309and 310, respectively, carried on a trolley 311. A motor 312 and gearreducer 313 are also mounted on the trolley and are operativelyconnected to rotate the mandrel 306 at a preselected constant speed. Thetrolley 311 itself is movably supported on a plurality of wheels 314which ride along rails 315 and 316 on each side of a pit 318.

An idler sprocket 319 is rotatably mounted at one end of the pit 318,and a drive sprocket 320 is mounted at the opposite end thereof to beselectively rotated by a DC motor 321.

A continuous, chain drive 322 extends around and between the sprockets319 and 320, and at least one link 323 thereof is secured, as at 324, toa foot flange 325 presented from the trolley 311. Thus, operation of theDC motor 321 determines both the rate at which, and the extent to which,the trolley 311 moves along the rails 315 and 316, and one manner inwhich to control the motor 321 is by the regulating cam drivenpotentiometer 326.

The cam driven potentiometer 326 is provided with a pinion 328 rotatedby a rack 329 which in turn carries a cam follower 330 at one end. Asecond sprocket 331 is provided on the output shaft of the motor 321 anda continuous chain 332 extends around sprocket 331 and a sprocket 333 onthe input shaft of a gear reducer 334. A cam 335 is affixed to theoutput shaft 336 of gear reducer 334 and communicates with cam follower330. Rotation of the cam 335 is preferably through 270° which causessufficient movement of the rack 329 and rotation of the pinion 328 forthe potentiometer 326 to vary the axial translation of the trolley 311while the mandrel 306 is rotating so as to achieve the desired leadangle. By changing the cam 335, the desired lead angle may be varied forthe continuous helical wrapping of the reinforcing strands upon themandrel. Of course, the gear reducer 334 enables cams of relativelysmall diameter, e.g., several inches (cm), to be employed despite axialreciprocation of the trolley 311 over many feet (m).

Thus, the aforedescribed, unique apparatus and method can produce novelFRP members in which the reinforcing strands of common hand are layed indiscrete layers and at pre-selected, constant, or varied, lead anglesand otherwise accomplish the objects of the invention. As will beapparent to those skilled in the art, combinations of the foregoingembodiments, such as the simultaneous variation of mandrel rotation andrelative axial movement between mandrel and winding head, may beemployed without departing from the scope of the invention.

I claim:
 1. A tubular fiber reinforced plastic member of variablediameter comprising: a resin base; a plurality of substantiallycontiguous individual reinforcing strands disposed in right and lefthand helices without longitudinal reinforcement; the individualreinforcing strands of each hand forming expanded helices having acontrolled predetermined lead angle of at least 10° at any point alongthe length of the member independently of the diameter thereof; thehelices of one hand being contained in at least one complete anddiscrete layer radially disposed of at least one complete and discretelayer comprised of the helices of opposite hand without interweaving ofthe strands comprising each of the separate layers.
 2. A tubular fiberreinforced plastic member as set forth in claim 1, in which the helicesof each hand have a pre-selected, constant lead angle throughout thelength of the member.
 3. A tubular fiber reinforced plastic member, asset forth in claim 1, in which the helices of each hand have a leadangle that is varied as desired along the length of the memberindependently of the diameter thereof in order to impart desiredstructural characteristics; and, in which the lead angle of the helicesin one layer is equal to the lead angle of the helices in each otherlayer at the corresponding longitudinal position along the length of themember.
 4. A tubular fiber reinforced plastic member, as set forth inclaim 1, in which the expanded helices have a lead angle falling withinthe range of from 88° to approximately 10°.